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Home My WebLink AboutSubsoils Report for Foundation DesignH-P\KUMAR 5040 Counry Hoad 154 Glenwood Spdnç. CO 8lô01 Phonc: (970) 945-7988 Fax (970) Sr45-845¡t Emal[ hpkgf anunodO ku¡narusa.com Geotechnical Engrneerng | Ëngineenng Geology Malerials ïesling I Environmenlal Ofllco Locatbns: Pefksr, Glgnü,ood Spdngs, and Sllv¡ilhome, Colondo SI,BSOIL STUDY rOR TìOT¡NDAîION DESIGN PROFOSED RBSIDENCE LOT a9,CORYELL RAI\¡CH SPIRIT MOT]NTAIN DRTVE GARFIELD COUNTY, COLORADO PROJECT NO. r6r-s2r NOVEMBER 8,2016 PREPARED FOR: KEN PHILLIPS 262l CASTILLA ISLE FORT LAUDERDALE, ILORTDA 33301 fkenphillius9@ qmail.com) TASLE OF CONTENTS PURPOSE AND SCOPE OF STUDY PROPOSED CONSTRUCTION SITE CONDITIONS STJBSIDENCE POTENTTAL............ FIELD EXPLORATION SUBSURFACE CONDITIONS ......... DESIGN RECOMMENDATIONS .,.... FOUNDATION AND RETAINING WALLS FLOOR SLABS....,. UNDERDRAIN SYSTEM SURFACE DRAINAGE LIMITATIONS FIGURE I - LOCATION OF EXPLORATORY BORINGS FIGURE 2 - LOGS OF EXPLORATORY BORINCS FIGURE 3 - LEGEND AND NOTES FIGURES 4 AND 5 . GRADATION TEST RESULTS TABLE I- SUMMARY OF LABORATORY TEST RESULTS .-l- I -t - )- 2- 3- -3- FOUNDATIONS ....- 3 - 4- 6- 6- -1 - 7- H-P t KUMAR Project No. 16.7.521 SITE CONDITIONS The vacant lot is vegetated with grass and weeds. The area has historically been used as irrigated pasture. The ground surface is relatively flat with a slight slope down to the nolthwest and on the order of I foot of elevation difference across the boring locations. Minor grading of the site occuned during subdivision development. An active irrigation ditch ís located along the eåstern lot line. SUBSIDENCE POTENTIAL Bedrock of the Pennsylvanian Age Eagle Valley Evaporite underlies the Coryell Ranch Subdivision. These rocks are a sequence of gypsiferious shale, fine-grained sandstone/siltstone and limestone with some massive beds of gypsum. There is a possibility that massive gypsum deposits associated with the Eagle Valley Evaporite underlie portions of the properry. Dissolution of the gypsum under certain conditions can cause sinkholes to develop and can produce areas of localized subsidence. During previous work in the area, several broad subsidence areas and sinkholes have been observed. These sinkholes appear similar to other.ç associated with the Eagle Valley Evaporite in areas of the lower Roaring Fork River Valley. No evidence of subsidence or sinkholes were observed on the property or encountered in the subsurface materials, however, the exploratory borings were relatively shallow, for foundation design only. Based on our present knowledge of the subsurface conditions at the site, it can not be said for certain that sinkholes will not deve lop. The risk of future ground subsidence at the site tkoughout the service life of the structure, in our opinion is low, however the owner should be aware of the potential forsinkhole development. If further investigation of possible cavities in the bedrock below the site is desired, we should be contäcted. FIELD EXPLORATION The fìeld exploration for the project was conducted on October 13 and 14,2016. Four exploratory borings were drilled at the locations shown on Figure I to evaluate the subsurface conditions. The borings were advanced with 4 inch diameter continuous flight augers powered H-PSKUMAR Prolect No. 16.2521 PURPOSE AND SCOPE OF STUDY This report presents the results of a subsoil study for a proposed residence to be located at t¡t 29, Coryell Ranch, Splrit Mountain Drive, Garfield County, Colorado. The project site is shown on Figure l. The purpose of the study was to dcvelop recommendations for the foundation design. The study was conducted in accordance with our agreement for geotechnical engineering services to Ken Phillips dated October 12,2016. A field exploration program consisting of exploratory borings was conducted to obtain information on the subsurface conditions. Samples of the subsoils obtained during the field exploration were tested in the laboratory to determine their classification, compressibility or swell and other engineering characteristics. The results of the field exploration and laboratory testing were analyzed to develop recommendations for foundation types, depths and allowable Pressures for the proposed building foundation. This report summarizes the data obtained during this study and presents our conclusions, design recommendations and other geotechnical engineering considerations based on the proposed construction and the subsurface condidons encountered. PROPOSED CONSTRUCTION Building plans for the proposed residence \ryere conceptual at the time of this study. In general, the residence will be single story wood frame construction possibly over a basement and with a detached shop building. Cround floors could be slab-on-grade or structural above crawlspace. Grading for this type of construction is assumed to be relatively minor with cut depths between about 3 to 9 feet. We assume relatively light foundation loadings, typ¡cat of the proposed type of construction. If building loadings, location or grading plans change significantly from rhose described above, we should be notified to re'evaluate the recommendutions contained in this report. H.P t KUMAR Projecl No. t6.7-521 -3- by a truck-mounæd CME4SB drill rig. The borings were logged by a represcnt¡tive of H-P/Kumar. Samples of the subsoils were taken with a l% inch LD. spoon sampler. The sampler was driven into thc subsoils at various depths with blows from a 140 pound hammer falling 30 inches. This test is similar to the standard penetration test described by ASTM Method D-1586. Thc penetration resistance values are an indication of the relative density or consistency of the subsoils. Depths at which the samples were taken and the penetration resistance values are shown on the logs of Exploratory Borings, Figure 2. The samples were rcturned to our laboratory for review by the projcct enginecr and testing. ST'BSURFACE CONDÍIIONS Graphic logs of the subsurface conditions encountered at the site are shown on Figure 2. The subsoils, below about 6 inchcs oftopsoil, consist ofnil to lVzteetofsandy silt and clay overlying dense, silty very sandy gravel with cobbles and boulders. Drilling in the dense granular soils with auger equipment was diffïcult due to the cobbles and boulders and drilling refusal was encountered in the deposit at Borings 3 and 4. Laboratory testing performed on samples obtained from the borings included natural moisture content and gradation analyses. Results of gradation analyses performed on smatl diameter drive samples (mìnus lr,å inch fraction) of the coarse granular subsoils are shown on Figures 4 and 5. The l¡boratory testing is summarized in Table l. No free try¡rter was cncountered in the borings at the time of drilling and the subsoils were slightly moist. DESICN RECOMMENDATIONS FOI.JNDATIONS Considering the subsurfacc conditions çncountered in the exploratory borings and the nature of the proposed construction, we recomrnend the buildings be founded with spread footings bearing on the natural granular soils. H-PÈ KUMAR Pro¡ecl No, 16.7-521 -4- The design and conslruction criteria presented below should be observed for a spread footing foundation system. l) Footings placed on the undisturbed natural granular soils should be designed for an allowable bearing pressure of 3,000 psf. Based on experience, we expect settlement of footings designed and constructed as discussed in this section will be about I inch or less. 2) The footings should have a minimum width of 16 inches for continuous walls and 2 feet for isolated pads. 3) Exterior footings and footings beneath unheated areas should be provided with adequate soil cover above their bearing elevation for frost protection. Placement of foundations at least 3É-inches below exterior grade is typically used in this area. 4) Continuous foundation walls should be reinforced top and bottom to span local anomalies such as by assuming an unsupported length of at least l0 feet. Foundation walls acting as retaining structures should also be designed fo resist lateral eârth pressures as discussed in the "Foundation and Retaining'Walls" section of this report, 5) All topsoil, sandy silt and clay and any loose or disturbed soils should be removed and the footing bearing level extended down to the relatively dense natural granular soils. The exposed soils in footing area should then be moistened and cornpacted. 6) A representative of the geotechnical engineer should observe footing ov¡or¡alinao n¡ia: ra ^^ã^Fàaáv^esrsl¡v¡¡d H¡lV¡ !V VVrrWltrtv IL'-^-Jl¡!^--LL,lll¡¡1¡UIl5. FOUNDATION AND RETAININC vfALLS Foundation walls and retaining structures which are laterally supported and can be expected to undergo only a slight amount of deflection should be designed for a lateral earth pressure computed on lhe basis of an equivalent fluid unit weight of at least 45 pcf for backfill consisting of the on-site granular soils. Cantilevered retaining structures which are separate from the H-P+ KUMAR Project No. 16.7.521 -5- residence and can be expected to deflect sufficiently to mobilize the fHll actìve earth pressure condition should be designed for a lateral earth pressure computed on the basis of an equivalent fluid unit weight of at least 40 pcf for backfill consisting of the on-site granular soils. Backfill should not contain organics or rock larger than about 6 inches. All foundation and retaining structures should be designed for appropriate hydrostatic and surcharge pressures such as adjacent footings, traffic, construction materials and equipment. The pressures recommended above assume drained conditions behind the walls and a horizontal backfill surface. The buildup of water behind a wall or an upward sloping backñll surface will increase the lateral pressure imposed on a foundation wall or retaining structure. An underdrain should be provided to prevent hydrostatic pressure buildup behind walls. Backfìll should be placed in uniform lifts and compacted to at least gA% ú the rnaximum standard Proctor density at a moisture content near optimum. Backfill placed in pavement and walkway areas should be compacted to at least 95Va of the maximum standard Proctor density. Care should be taken not to ûvercompact the backfill or use large equipment near the wall, since this could cause excessive lateral pressure on the wall. Some settlement of deep foundation wall backfill should be expected, even if the mater¡al is placed correctly, and could result in distress to facilities constructed on the backfill. The lateral resistance of foundation or retaining wall footings will be a combination of the sliding resistance of the footing on the foundation materials and passive earth pressure against the side of the footing. Resistance to sliding at the bottoms of the footings can be calculated based on a coefficient of friction of 0,50. Passive pressure of compacted backfill against rhe sides of the footings can be calculated using an equivalent fluid unit weight of 400 pcf. The coefficient of friction and passive pressure values recommended above assume ultimate soil strength. Suitable factors of safety should be included in the design to limit the strain which will occur at the ultimate strength, particularly in the case of passive resistance. Fill placed against the sides of the footings to resist lateral loads should be a granular soil compacted to at least957o of the maximum standard Proctor densïty at a moisture content near optimum. H.PÈ KUMAR Projecl No, 16-7.521 -6 FLOOR SLABS The natural on-site soils, exclusive of topsoil, are suitable to support lightly loaded slab-on-gradc construction. To reduce the effects of some differential movement, floor slabs should be separated from all bearing walls and columns with expan.sion joints which allow unrestrained verticâl movement. Floor slab control joints should be used to reduce damage due to shrinkage cracking. The requirements for joint spacing and slab reinforcement should be established by the designer based on experience and the intended slab use. A minimum 4 inch layer of free- draining gravel should be placed beneath basement level slabs to facilitate drainage. This material should consist of minus 2 inch aggregate with at least 50% retained on the No.4 sieve and less than?Vo passing the No. 200 sieve. All fill materials for support of floor slabs should be compacted to at least 95Vo of maximum standard Proctor density at a moisture content near optimum. Required hll can consist of the on- site granular soils devoid of vegetation, topsoil and oversized rock. UNÐERDRAIN SYSTEM Although free water was not encountered to the exploration depth of I I feet, it has been our experience in the area that local perched groundwater can develop during times of heavy precipitation or seåsonal runoff. Frozen ground during spring runoff can also create a perched condition. We recommend below-grade construct¡on, such as retaining walls, crawlspace and basement areas, be protected from wetting and hydrostatic pressure buildup by an underdrain cvslêrn I)llrino lhe h:rccrncnt evnnvntinn nrl¿{irinnql evnlnrnfinn chnrrlá lra a¿rFn,ma¡l tn rr¡.lfrr ---...1¡ ¡.t Éee.¡¡v¡.e ¡¡ u¡¡vg¡u vs l/v¡av¡¡r¡vs fv vv¡a¡J groundwater level is not within 5 feet of the basement floor slab. The drain should consist of drainpipe placed in the bottom of the wall backfill surrounded above the invert level with free-draining granular mater¡al. The drain should be placed at each level of excavation and at least I foot below lowest adjacent finish grade and sloped at a minimum l?o to a suitable gravity outlet, drywell or sump and pump. Free-draining granular material used in the underdrain system should contain less than 29o passing the No. 200 sieve, less tlran 507o passing H-P * KUMAR Projecl No. 16-7-521 -7- the No. 4 sieve and have a maximum size of 2 inches. The drain gravel backfill should be at least lYz feet deep. SURFACE DRAINAGE The following drainage precautions should be observed during construction and maintained at atl times after the residence has been completed: l) Inundation ofthe foundation excavations and underslab areas should be avoided during construction. 2, Exterior baekfill should be adjusted to near optimum moisture and compacted to at least 957o af the maximum standard Proctor density in pavement and slab areas and to af least 9OVo of the maximum standard Proctor density in landscape areas. 3) The ground surface surrounding the exterior of the building should be sloped to drain away from the foundation in all directions. \üe recommend a minimum slope of 6 inches in the first l0 feet in unpaved areas and a minimum slope of 3 inches in the first I0 feet in paved areas. Free-draining wall backfill should be capped with about 2 feet of the on-site finer grained soils to reduce surface water infiltration. 4| Roof downspouts ând drains should discharge well beyond the limits of all backfill. 5) Landscaping which requires regular heavy iruigation should be located at least 5 feet from foundation walls. LIMITATIONS This study has been conducted in accordance with generally accepted geotechnical engineering principles and practices in this arca at this time. 'We make no w¿uranty either express or implied. The conclusions and recommendations submitted in this report are based upon the data obtained frorn the exploratory borings drilled at the localions indicated on Figure 1, the proposed type of construction and our experience in the area. Our services do not include determining the presence, prevention or possibility of mold or other biological contaminants (MOBC) developing H-P * KUMAR Proþt No. 16.7-521 .8- in the futurc. If thc client is concerncd abu¡t MOBC, then a professional in this special ficld of practicc should bc consulted. Our findings include interpolation and cxtrapolation of the subsurface conditions identificd at the exploratory borings and variations in the subsurface conditions may not become evident until excavation is performed. If conditions encountered during construction appear differcnt from those described in this report, we should be notified so that re-evaluation of the recommendations may bc made. This report has been prcparcd for the exclusive use by our client for design purposes. We are not responsible for technical intcrprctations by others of our information. As the project evolves, we should provide continued consultation and field services during construction to rev¡ew and monitor the implementation of our recommendations, and to verify that the recommendations have been appropriately interpreted. Signifïcant design changcs may rcquire additional analysis or modifications to the recommendations presented herein. Wc recommend on-site observation of excavations and foundation bearing strata and tcsting of structural fill by a ¡Epresentative of the geotechnical engineer. Rcspectfully Submitted, H-PtKUMAR ú{þ Shane M. Mello -Staff Ëngineer Reviewed by: Steven L. Pawlak, P.E. SMM/ksw H-Pt KUMAR Project No. 16-7-521 i¡ tåù t SPIRIT MOUNTAIN ROAD LOT 25 -l APPROXIMAÏE SCALE-FEET LOr28 . BOHING 1 O BOR]NG 2 (. BORINü 4 O BORINGS LOT 29 ) _ry,r:,y:qPf!'yt- ¿1¿¿ L--'- 1 6- 7-521 H-PryKUMAR LOCATION OF EXPLORATORY BORINGS Fig. 1 t t ¡ a FOFING I BORING 2 BORINB 5 BORING 4 o o 8e112 5O1t 9t t2t.8 =0.9 5 55/12 2AO=12 lt s t- l,^¡ u IË d-l¡l cr l2 12/t2 67 /t2 l¡¡t¡¡fa. I¿ ô_ ¡¡¡c¡ t.5 1=17 t6 -10 32/tZ t07s/t2 r5 t5 1 6-7-521 H-PVKUTVIAR LOGS OF EXPLORATORY BORINGS Fís. 2 LEGEND ñ n w I TOPSOIL¡ ORGANIC SILT ANO Cl¡Y, FIRM, SLICHILY HOIST, BROWN. SILT ÀND CLAY (ML-CI); SANDY. PRO9ABLE GRAVEL, STIFF. SLIGHTLY lJotST. BROWN. GRAVEL ANO COBBLES (CU); VgRl SÂNDY. SILTY. DENSE, SLÍGHTLY tdOtst, },iIXED BROWN. ROUNDED ROCK. gR¡vE sAMqlE¡ STÂNDARO PENETRÀT|oN TEST (sPT), 1 5/8 tNcH t.D. spltT sFooN sÄMPLE. ASIM D-t586. q57¡2 DRIVE SAMPLE BLOW COUNT. INOICATES THAI 56 ALOWS OF A |4o-POUND HAMMER--,'- FALLING 30 INCHES WERE REQUIREO TO DRIVE THE SFT SAMFLER 12 INCHES. I PRACÍICAL ÀUGER REFUSÀI. NOTES- THE EXPLORATORY EORINGS WERE ORILLED ON OCTOBER 15 AND 14.2016 wlTI{ A 4-INCH OIAMETER CONTINUOUS FLIGHT POWER AUGER. 2. THE LOCÀTIONS OF THE EXFLORATORY BOßINGS WERE MEASURED APPROXIMÀTELY BY PAGING FROM FEATURES SI{OWN ON TI{E SITE PLAN PROVIDEO. 3 THE ELEVÂTIONS OF THE EXFLOñATORY SORINGS WERE HCIT MEASURED ANO THE LOG5 OF THE EXPLORATORY AORINGS ARE PLOIIEO TO OTPTH. 1, TH€ Ð(PLORATORY gORfNG LOCATIONS SHOUTD BE CONSIOEßEÐ ACCURATE ONLY IO THE DEGFEE IMPLIEO BY THE METHOD USEO. 5. THE LINES B€TI/ÍEEN MATERIALS SHOWI{ ON THE EXFTORATORY BORING LOGS REPR€SENT THE APFROXIMATE BOUNOARIES SETWEEI,I MÀTERIAL TYPES ANO THE TRANSITIONS MAY BE GRADUAL. 6. GROUNDWÀT€R WÂS NOT ENCOUNTERED IN THE SORINGS AI THE T]ME OF ORILLING. 7. ]¡SORATORY TESI RESULTS! WC = WATER CONTENT ('T} (ASTM T 221É}i+1 = PERCENTAGE RETAINE0 ON NO. 4 SIEVE (ASTM 0 -ZoQ= PÊRCËNTAGE PASSING NO. 200 SIEVE (ASTM 0 1 a22)i 4o)l 1 6-7-52t H.PryKUTVIAR LEGEND ANO NOTES Flg. 3 d II stcvf. aa{aLYsts SANO GRAVEL FINE M€DrUM JCOARSE ¡INE COARSF r{Yoior¡flfi ^NÀtYtr¡ t ! re t0 ¡û 7i a¡ 50 ¿0 lo ¡û rû t9 æ t0 40 !o IO t! .D to I 0t¡ I E TE o otÂM OF CLÃY TO SILT COEELES GRÂVEL 50 Z saNo t8 ,4 SItÏ AND CLAY I2 X SAllPlf OF: 5llly. V¡¡t Soody 0rovrl FnOM: 8o.lng I O 2,5 f 5' eembl¡rd 10Ê rË !0 tô æ 5t a0 !0 t3 !g o IQ tg ¡0 l !I T ,OE ! ,ot t0 a0 toı OF IN CLAY TO SILT COEBLES GRÂVEL '7 X SANÐ T7 X SrtT ÁN8 CLÀY t6 X fn0u: Aodtrg ? O 5 ¡ l0' ccmblnrd lh¡r¡ l¡rl latull¡ aFplt .ñlt 16 th..oñÞlar rhlÊh rr.. l.¡|.d, fhrhrlhg r.Þc., rhe¡t nol b. r.prcC!c.d, BEaÉl l. l!l¡, rllh!úl lhr r.fll.ñ aþ9Erol ol Xuñd I ^rto.ja?ar, lñê.5;.rr ınolttl¡ |{t¡ñg ¡r pclod.d lâ4c.rCc¡o. ¡llh ASfl¡ 0a22. ASl¡¡ Cll6 !ñð./or åstr 0ll¡0, HYOiOT¡ûEn ðtALYStç SIEVE ¡NILYIIS u.l. gAND GRAVEL FINE UEþIUM ICOARSE FINE coagSt SAMPLÊ Of: Sllly vrry Sondy Grcvd 1 6-7-5? 1 H.PryKUIMAR GRADATION TEST RESULTS Fig" 4 ¿ ¡: ANALYS 3 s'e vE sÂNo GRAV€L rINE H¿DruM lcoÂRsE rINÊ COARSE I T Ë t8 lo l0 ra 6 l¡ ¡c t0 tû to 0 o to z9 t0 ¡o ¡! ao ?Ò ag to r¡û ¡ E II CLÀY TO SILÎ co3åtgs cñÀvEL 50 x sailo t9 ,¿s¡LT AND çtAY 11 X Sl¡llPLF 0f: Sllly vrr¡ Sondy ûrovrl fR0ti¡: 8Èrlñ! I e 23 ü å' ¿oñblñrd fh.r. t.¡t rtultt applt c¡lt r. th. ¡qmÞla¡ rhlah *a,r tarlad. th¡t.¡tlûg tpcrl rhcll not ùr rtprods.d,a¡ç.pl lñ ,!lr, rltholl lh. r.ftl.¡c¡tFral af X!6!, I ¡trscillar. lñçll.w a¡lltr¡. l.tl¡ôg lr Þ.'lom¡d ln ÉÊÉor¿!nç. rilh lSfll D¡2¡. ASt¡¡ C|JS cnd¡/cr rflt¿ Oll¡0, 16-7-521 H-PæKUMAR GRADATION TEST RESULTS Fis. 5 H-P*KUMAR TABLE 1 SUMITIARY OF LABORATORY TEST RESULTS ProjectNo. 1È7€21 son-oR SEOROCKTVPE Silty, Very Sandy Grar¡el Silty, Very Sandy Gravel Silty, Very Sandy Gravel UNCONRNËD COITIPRESSIVE STRENGTH {PSFI Pl¡SnC ll,¡oE¡( lU"l LIQUID LllilT lral 38 t2 PERCENl PASSING ilo.200 SIEVE l6 I I TION SANO (v.l 37 39 GRAI GRAVEL t%t 50 47 50 NATURAL DRY oENStnr locO NATURAL TOISTURE coilTEr¡T tlLt 1.8 t.3 0.9 OEPTH afrt zt6+ 5 combirred 5+10 combined 2Y¿+ 5 combined AOËNG I t 4